1. Field of the Invention
The present invention relates to a radio transmission apparatus, a radio reception apparatus, a transceiver, and a radio communication method.
2. Description of the Related Art
Methods for radio communication in a very wide frequency band called Ultra Wideband (UWB) has been developed in radio communication fields in recent years. Although development of a 4-GHz band called Low Band in the UWB has been emphasized in related art, it is necessary to shift the development field from the Low Band to High Band (6 GHz to 10 GHz) in order to support the coexistence with various communication methods.
In such a situation, multiband orthogonal frequency division multiplexing (OFDM) developed by an industry organization called WiMedia has become mainstream. In the multiband OFDM by the WiMedia, the UWB bandwidth is divided into frequency units of about 1.5 GHz. Each frequency unit is called a band group (BG).
FIG. 41 illustrates band groups defined by the WiMedia. Of the band groups in FIG. 41, a band group #1 is allocated to the low band and band groups #3, #4, #5, and #6 are allocated to the high band. Of the band groups in the high band, the band group #5 is assumed to be used for special applications because the band group #5 has higher frequencies and the bandwidth of only 1 GHz is allocated to the band group #5. Accordingly, the challenge is to design radio apparatuses supporting the band groups #3, #4, and #6 as general high band products.
As illustrated in FIG. 41, each of the band groups #3, #°, and #6 in the high band is further divided into three bands each having a bandwidth of 528 GHz. High-speed hopping among the three bands is defined in the WiMedia specifications.
It is noted that the hopping causes various problems in analog circuit design of the radio apparatuses. Specifically, the problems concern direct current (DC) offset by the hopping and phase continuity of oscillators. For example, Japanese Unexamined Patent Application Publication No. 2005-129993 discloses a method of resolving problems of direct-conversion transmitter-receivers by producing the multiband OFDM UWB transmitter-receivers in Low Intermediate Frequency (Low IF) configurations. Japanese Unexamined Patent Application Publication No. 2006-121546 discloses a method of acquiring the center frequency of each band in frequency synthesis apparatuses for the hopping without any error in phase or amplitude.